<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .taiji {
        margin: auto;
        margin-top: 400px;
        width: 400px;
        height: 400px;
        border-radius: 50%;
        /* border: 1px solid black; */
        box-sizing: border-box;
        border-color: black;
        border-style: solid;
        border-width: 1px 1px 200px 1px;
        position: relative;
      }
      .taiji::before {
        content: "";
        width: 50%;
        height: 200px;
        top: 100px;
        left: 0;
        position: absolute;
        background-color: black;
        box-sizing: border-box;
        border: 50px solid white;
        border-radius: 50%;
      }
      .taiji::after {
        content: "";
        width: 50%;
        height: 100%;
        top: 50%;
        right: 0;
        position: absolute;
        background-color: white;
        box-sizing: border-box;
        border: 50px solid black;
        border-radius: 50%;
      }
    </style>
  </head>
  <body>
    <div class="taiji"></div>
  </body>
</html>
